Electrical measuring instrument



- WWI/W Jan. 21, 1941. TRUAX I 2,229,399

ELECTRICAL MEASURING INSTRUMENT Fil'ed Jan. 5, 1939 III I I Patented Jan. 21, 1941 UNITED STATES PATENT OFFICE 2 Claims.

This invention is directed to electrical measuring instrumentatand particularly to the type of instruments known as repulsion type voltmeters and ammeters. In an instrument of this structure which makes provision for the inclusion of a damping chamber and a spool or core for the winding of a coil and the mounting of the movable portions of the instrument; and the principal object of the present invention is to provide such a mounting composed of a minimum number of parts and so arranged and constructed that the device as a Whole may be easily assembled as a unit for mounting upon a dial board or other support for the instrument.

A further object is to so construct the parts that when assembled they will be firmly and rigidly connected so as to maintain the bearings in the proper alignment and to afford space for the mounting and movement of the pointer and associated parts.

Further objects and details will appear from a description of the invention in conjunction with 25 the accompanying drawing, wherein i Figure 1 is a perspective view of the fully assembled instrument mounted upon a panelboard or the like;

Fig. 2 is a perspective plan view looking down into the interior of the lower section of the frame which affords the damping chamber;

Fig. 3 is a side elevation of the pointer shaft and pointer; and

Fig. 4 is a view of the screw posts which afford a mounting for the frame sections and also provide the electrical connections required.

It is preferred to make the sections of the frame or mounting from insulating material which is preferably molded to the intended shape.

The frame as a whole comprises a base section 5 of open drum shaped formation, comprising a cylindrical side wall 6 and a flat bottom. 1. On diametrically opposite sides the base section is provided with outwardly extending ears 8, the under surfaces of which lie flush with the under surface of the bottom and constitute projections therefrom. Each ear is provided with an aperture 9 for the reception of a vertical post it, re-- quired for holding the parts in assembled relation.

The base section on its interior is provided with inwardly tapering wedge-shaped blocks II which in the center merge into segmental center blocks I2 of lesser height than the surrounding wall of 55 the base section, and the two converging blocks I l character it is customary to provide a frame 7 terminate short of the center, which is provided with a vertical aperture l3 which affords a socket hole for the reception of the spindle shaft M which carries the pointer 15 at its outer end.

The shaft is provided with a pair of vanes it which are suspended from a cross bar ll passing through the shaft, at a proper elevation to permit the vanes to oscillate to a limited degree, within the spaces provided within the base section, 10 which spaces in conjunction afford a damping chamber for limiting the oscillation period of the moving element, the movement of the vanes being retarded by air pressure in a manner well understood in the art.

The cavity in the lower frame section is closed by the upper frame section l8 which is of spool shaped formation comprising spaced circular upper and lower plates i9 and 20, and a neck of lesser diameter which afiords a core for the winds ing 2f, the spool as a whole being of molded insulating material and of across diameter substantially equal to that of the base section 5, so that the parts when assembled will afford an instrument of substantially uniform diameter throughout.

In order to provide for a proper positioning and assembling of the upper section in register with the lower section, the plates l9 and 20 are each provided with oppositely disposed protuberant ears or lugs 22 which are apertured to receive the posts Ii), the apertures all aligning, so that when the posts are entered therethrough, the upper and lower sections of the instrument will combine to afford a rigid mounting for the operating parts.

The posts H3, at their upper ends 23, are enlarged to afford shoulders for clamping contact with the uppermost lugs 22, and each of the posts at its upper end terminates in a reduced threaded stem 24 adapted to project through the associated end of a bridge bar 25 of insulating material which spans the center of the upper or spool section of the instrument and stands in elevated relation thereto.

The projecting ends of the stems 24 have screwed thereon clamping nuts 26, and the lower end 2'! of each post H3 is threaded to receive a nut 28, so that when the posts are entered through the base 29 of a casing or other mounting, and the nuts 26 and 28 are tightened, the sections of the instrument will be held tightly in assembled relation and the instrument as a whole will be rigidly mounted in position upon the panelboard, or other equivalent mounting.

The upper pointed end of the spindle shaft I4 is journalled within a bearing stud 30, and the shaft has entered therethrough the hollow stem 3| of a pointer 32, which occupies a position slightly above a transversely extending cross pin 33 which is also entered through the spindle shaft. A coil spring 34 has one end secured to the shaft and its opposite end is soldered to a spring clip finger 35 carried by the bridge bar, which completes the mechanical assembly.

The terminal wires 36 of the coil are entered through the top plate of the spool section and soldered to the enlarged shouldered portions of the posts, which latter, being of conducting material, subserve the double function of tie rods and conductive elements, being entered at all points through insulating material, so that additional means for insulating the parts are unnecessary.

In assembling the various portions of the instrument, the lower end of the spindle shaft will first be mounted in the socket provided therefor in the bottom of the base section, after which the spool section with the winding thereon will be positioned with the apertured lugs or ears in register with those on the base section, and the posts will be entered through said apertures, thus firmly uniting the upper and lower sections and effectively closing the damping chamber by the cap or cover afforded by the bottom of the spool section. Thereafter, the bridge bar will be properly positioned to afford a bearing for the upper end of the spindle shaft, and the spring and terminal wires soldered or otherwise rigidly secured.

With the nuts at opposite ends of the posts tightened, the entire instrument will assume the form of a fully assembled unit for shipment or otherwise.

The invention as a whole is of extremely simple construction, with the parts so formed as to insure exact registry with one another, and being constructed of a minimum number of parts the possibility for mal-adjustment is practically eliminated.

I claim:

1. In an electrical measuring instrument of the class described, a frame comprising a lower base section and an upper spool section, the base section being of cylindrical drum shaped formation and open at its top and affording on its interior a damping chamber and planate on its bottom to fit against a plane surface, oppositely disposed apertured tongues extending outwardly from the base section, the spool section comprising upper and lower plates and a connecting spool portion of less diameter, the upper and lower plates being provided with outwardly extending ears having apertures registering with those first mentioned, posts extending through said apertures and projecting above the spool section and below the base section, a bridge bar having its upper ends mounted upon the projecting ends of said posts, a spindle shaft provided with a pointer and journalled at its lower end in the base section, a bearing carried by the bridge bar for the upper end of the spindle shaft, a coil winding for said spool section having its ends respectively connected with said posts, the posts being of conductive material, and clamping means on the upper and lower ends of said posts for clamping the base section, the spool section and the bridge bar in assembled relation, the posts being adapted to serve as electrical connectors with a source of power.

2. In an electrical measuring instrument of the class described, a frame comprising a lower base section and an upper spool section, the base section being of cylindrical drum shaped formation and open at its top and closed at its bot tom and affording on its interior a damping chamber, apertured members extending outwardly from the base section, the spool section comprising upper and lower plates and a connecting spool portion of less diameter, the upper and lower plates being provided with outwardly extending members having apertures registering with those first mentioned, posts extending through said apertures and projecting above the spool section and below the base section, a bridge bar having its ends mounted upon the projecting upper ends of said posts, a spindle shaft provided with a pointer and journalled at its lower end in the base section, a bearing carried by the bridge bar for the upper end of the spindle shaft, a coil winding for said spool section, and clamping means on the upper and lower ends of said posts for clamping the base section, the spool section, and the bridge bar in assembled relation.

LAWRENCE E. TRUAX. 

